1. Field of the Invention
The present invention relates to an apparatus for performing assays in conjunction with an optical bio-disc. The invention further relates to methods for separating, immobilizing and/or detecting micro-particles or beads, cells, labels, or tags using a density gradient and/or centrifugation to perform an assay
2. Discussion of Background Art and the Present Invention
There is a significant need to make diagnostic assays and forensic assays of all types faster and more local to the end-user. Ideally, clinicians, patients, investigators, the military, other health care personnel, and consumers should be able to test themselves for the presence of certain factors or indicators in their systems, and for the presence of certain biological material at a crime scene or on a battlefield. At present, there are a number of silicon-based chips with nucleic acids and/or proteins attached thereto, which are commercially available or under development, for performing biomedical, chemical, or biochemical assays. These chips are not for use by the end-user, or for use by persons or entities lacking very specialized expertise and expensive equipment. It is an object of the present invention to obviate or mitigate at least one of these disadvantages by use of a relatively inexpensive assay system that can be used by the end user without specialized training.
Many biochemical techniques exploit the mutual interaction of antigens and antibodies, hybridization between complementary strands of DNA, or protein affinity. Some of these may include streptavidin and biotin, along with the use of labeled reagents. A variety of labels or tags have been employed for detection. Examples include enzymes, color-based, radioactive, phosphorescent, fluorescent and chemiluminescent reagents, microspheres, metal colloids, as well as fluorescent dyes such as fluorescein and rhodamine. Fluorescent anti-human IgG, for example, is routinely used as a labeled reagent.
A “sandwich” immunoassay is performed in one embodiment of the present invention wherein a doubled layer procedure is designed to detect a specific antibody or antigen. For example, to detect the presence of an antibody in a sample, a corresponding antigen is first immobilized onto solid substrate. The immobilized antigen is then exposed to the sample being tested. Some or all of the antibodies present will bind to the immobilized antigen. Any excess or unbound antibody is washed away.
A labeled reagent such as fluorescent anti-IgG is then added to the sample. The labeled reagent binds to the antibody and any excess reagent is washed away. The intensity of the fluorescence is then measured to provide an indication of the quantity of antibody present in the sample.
One of the problems with “sandwich” immunoassays is that a number of washing steps are involved. The washing steps are necessary to remove the excess antibodies and labeled reagents, which would otherwise have an adverse effect on the accuracy of the results.
A further problem is that a sample may only be analyzed for one target at a time. Therefore, to detect a number of different targets in a sample, separate sample containers are required. As a consequence, a large number of washing steps are necessary, making the procedure cumbersome and time-consuming.
It is an object of the present invention to obviate or mitigate at least one of the abovementioned disadvantages.
It is a further object of the present invention to reduce or eliminate the number of washing steps that are presently required to conduct an immunoassay.
The objectives mentioned above are achieved by providing a device for conducting a chemical, biochemical, or biomedical assay that is adapted to be used in conjunction with a disc-based scanning device. One such device is described, for example, in U.S. Pat. No. 5,892,577, entitled “Apparatus and Method for Carrying out Analysis of Samples”, which is incorporated herein by reference in its entirety.